Grinding wheel assembly



July 23, 1957 e. F. KEELERIC GRINDING WHEEL ASSEMBLY 2 Sheets-Sheet 1Filed Nov. 25, 1953 U. II VI,

July 23, 1957 G. F. KEELERIC GRINDING WHEEL ASSEMBLY 2 Sheets-Sheet 2Filed Nov. 25, 1955 the diamond'powder. 1 great deal of cutting, thelife of such tools'is shorter than conventional diamond grinding wheelsof the prior United States Patent GRINDING WHEEL ASSEMBLY George F.Keeleric, Dundee, Ill.

Application November 25, 1953, Serial No. 394,349

4 Claims. (Clf51-209) This invention relates to abrasive tools and hasas its general purpose the making of fast-cutting abrasive tools ofgreat accuracyand of'verylow cost. It has particular value inapplications where costly diamond powder is used as the abrasive,although it is not confined to this 2 application.

In diamond grinding, it has been the practice to provide Ydiamond-bearing grinding 'wheels, usually made with powdered metal orvitrified or plastic bond. These grinding wheels must be made withaccuracy if accurate grind- T he single-layer diamond wheels, such asthose made .inaccord'ance with my Patent No. 2,368,473, issued Janu'ary'30, 1945, for Method of -Making Abrasive Articles, 7 also have requiredcareful truing up. This requires several costly operations inmanufacturing, and it requires labor and care atthe point of use.Thefact is, however,

that-the working part'of these single-layer diamond grind ing wheels'canbe'made quite inexpensively-4f the costly operations of making themounting wheels is-not ineluded.

'Also, it has been found that such single-layer diamond grinding wheelswill cut at'very high rates if the diamond particles are arrangedproperly, as for example in my co-pending application: Serial No;357,483, filed 'May '26, 1953, now abandoned, for Abrasive Tool andMethod of Making Same, or in the continuation thereof, Serial No.394,348, filed November 25, 1953, for AbrasiveTool andMethod MakingSame.

Such arran'gements result in the use ofvery few diamond particles ineach tool, and this, of course, reduces their cost. It results in a verycomplete and efficient use of But since each particle does a art.Accordingly, it is desirable to find a means of avoiding the'makingofcomplete grinding wheels in order to replace a consumable portionwhich represents only a part of the cost of a complete wheel.

The object of this invention is to provide a way of meeting theconsiderations 'just stated.

More particularly, it is an object of this invention'to provideremovable and replaceable diamond grinding elements of great accuracywhich are inherently easy and cheap to make.

Another object is to provide for quick and easy removal of-one of theabrasive-surface elements and its replacement by another.

Another object isto provide thin, light, flexible rings carryingabrasive particles and responsive to the magnetic attraction of amagnetic chuck.

2,799,980 Pate'nted Jul 23, 1957 A somewhat different object is achievedat the same time. This is a cushioning or shock-absorbing efiectwhichgives what operators call a sof feel. Experienced operators reportthatsome diamond grinding wheels have a soft feel; others a hard feel. Thus,the so-called resinoid or plastic-bonded wheels have a soft feel, whilecertain metal-bonded wheels have a hard feel. The soft feel is muchpreferred, and this seems to be more 1 vthan-whim, for sharper edges canbe produced with a soft wheel. This may be because the softer bondingmaterial yields somwhat as the abrasive particles engage the work, andthus reduce the grinding shock so that the edges of the workpiece beingcut' are not roughened by tiny nicks chipped away by the impact of theabrasive particles.

- Butwhetheror not this analysis is correct, his com- -merciallydesirable to obtain the soft feel in such grinding wheels.

Yet there are many advantages to a hard metal bond, particularly thefact that better holding of abrasive particles is obtained, thusreducing the waste resulting from dislodgement of'particles. And it isan object of this invention to obtain a soft feel while retaining theadvantages-of a metal bond in holding the abrasive particles.

The crux of the invention lies in making a thin ring or annulus ofnickel-or iron, which serves as a bond for the abrasive particles, andin making a cooperating chuck with appropriate interlocking means whichpermits rotary "slippage but, at the same time, centers the ring on thechuck and prevents its' fiying off under use. The interlock arrangementintentionally provides for a slight pared with complete grinding wheels.

amount of rotary or circular slippage of the ring relative to the chuck,so as to minimize grinding shock and give a'soft feel. 'The low mass ofthe abrasive-bearing ring is a factor in achieving this result.

rings can be reclaimed for'further use after the abrasive 7 that is,they need not themselves be magnets.

particles are worn'down', and this is another object.

Other objects will appear in the description of the invention whichfollows.

In the drawings: Fig. 1 is a perspective view of an abrasive-bearingring of th1s invention.

Fig. 2 is a sectional view of a magnetic chuck made to cooperate withthe ring of Fig. 1, taken along the line AA of Fig. 3 and showing theabrasive-bearing ring of Fig. 1 in place.

Fig. 3 is a sectional view taken along the line B-B of Fig. 2 andshowing virtually a plan view of the magnetic chuck.

Fig. 4 is a plan view, partly in phantom, of a modified form of chuck.

Fig. 5 is a sectional view, partly in phantom, of the chuck of Fig. 4taken along the line CC.

Referring to Fig. 1, the ring proper 1 is preferably made of nickel oriron or other material, which will be held by the magnets of a magneticchuck. Such materials are referred to here as magnetic, although theyare so only in the sense of being attracted by magnetic force;

Protruding from the working surface of the ring 1 are abrasive particles3, which are imbedded in and held by the metal or a portion of it. Theseparticles are shown much enlarged in Fig. 1. In actuality they arescarcely visible except as bright points of reflected light. If it ispreferred,

to permit this.

"to use a material like bronze as a bonding metal, this'may be done, andthen an iron or nickel ring may be soldered to it. It is desirable tokeep the thickness of the ring to a minimum in order to save cost, toreduce mass and,

' also, to minimize any problem of rotating unbalance.

In practice,the rings may be less than %& in thick- J ness and still bestrong enoughto be easily handled.

Moreover, if the metal is thin enough and flexible enough,

it will be flattened by magnetic attraction of the chuckand will runtrue. The same result in this respect-might be obtained by making thering thick enough and rigid enough so that it 'will not be distorted,but this is not preferred. What must be avoided is to make the ring justweak enough asto'be easily bent slightly out of shape by handling yetnot flexible enough to be pulled flat when laid against the magneticchuck.

- 7 Depending from the surface of the ring opposite the abrasive-bearingsurface arethree studs 5. These may take the form of round pins, asshown, and. may be soldered, brazed or resistancewelded (e. g., spotwelded or projection welded) to the ring 1. It is preferable thatwelding'be used and that the studs 5 be of the same material as ring 1.Or they may take the form of segments of a ring of rectilinear sectionand may register with an annular slot in the magnetic chuck.

It isimportant that the ring 1 be of uniform thickness from its workingsurface to its chuck-engaging surthe way around the ring.

. a The ring 1 may be made following some of the disclosure of myaforementioned Patent No. 2,368,473, and

achieved in other ways; for example, the ring may be made of powderedmetal, following the usual molding and sintering practice. Nickel powderor iron powder or various combinations which provide a magnetic materialmay be used. Or a thin bonding layer of bronze powder may be used, whichwill then be backed up by a ring of nickel or iron or other magneticmaterial, the two parts being attached by soldering or sintering orcementing. It has been found, however, that the electrolytic methodgives an excellent result. Attention should also be given to the factthat one of the important uses of the invention lies in theestablishment of an arrangement of a relatively small number of diamondparticles on the working surface of the ring, preferably arranged in adesirable cutting pattern, all with the intention of increasing thecutting rate but with the recognition that the life of the workingsurface is thus reduced.

Once the ring has been ground or otherwise Worked to a'uniform thickness(in the circular sense) then the interlocking studs 5 are attached. Thestuds and the ring are located in a suitable jig and welded or solderedwith 400 F;. solder.

' It will be seen that by this means a very inexpensive abrasive elementis produced, characterized'by great accuracy in the uniformity ofthickness.

Turning now to the chuck with which the ring coi operates, the bestgeneral understanding will be had by reference to Figs. 2 and 3 takentogether.

A-strong wheel body 11, made of brass, aluminum or other non-magneticmaterial, is machined to provide a center aperture '13, four mountinghole 15, and eight 7 tapped truing holes 17. If desired, the truingholes may be omitted and the truing accomplished by shims between thewheel member 11 and the mounting plate of a grinding machine, all in theconventional way. The center aperture is adapted to fit closely over theend of a grinding spindle which ordinarily protrudes from a mounting mayembody the invention of the continuation of my aforesaid co-pendingapplication, Serial No. 357,483.

Thus, a carefully made plating blank is coated with adhesive, and apattern of diamond particles is placed on it. Then, a thin layer ofcopper is electrolytically deposited through the adhesive, which must bethin enough The copper layer is usually only a few thousandths of aninch thick-sometimes less than one plate fastened to the spindle. Themounting plate is conventionally provided with four tapped holes whichall register with the mounting holes 15. In practice, the

I chuck is slipped over the end of the grinding spindle and against themounting plate, and screws or bolts are passed through holes 15 andscrewed into the tapped holes in thousandth.v In any'case, it willcoverthe particles to ment of any supporting iron ring or other specialprovision to this end. .At some later stage in the operations, the thinlayer of copper is removed so as to expose the abrasive particles to adepth equal to the thickness of the copper.

The back surface of the nickel is then ground flat and smooth in agrinding machine. This may be done most advantageously before the nickelring is stripped from the plating blank. The blank carrying the nickellayeris set on the table of a surface grinder with the nickel toward thegrinding wheel. Since the blank is itself carefully made and of uniformand known thickness, the grinding operation can be used to establishboth the desired dimension and uniformity of thickness in the ring.

' After this operation, the,ring may be stripped from the blank and isfinished except for adding studs 5 and removing the thin copper layer.

It is possible, of course, that the .same. result may be the mountingplate.

The wheel body 11 has an upraised portion around its periphery intowhich a groove 19 is cut to a depth of about /8 and to a width topermit'receiving a number of U-shaped, permanent magnets 21. Each ofthese magnets is fastened by a screw 23 to the wheel body 11. Themagnets are arranged in a shifting pattern of polarity as indicated bythe designations N and S on the pole faces (Fig. 3). V

The groove 19 is adapted to hold, in addition to the magnets, threebrass inserts 25 fastened with screws or rivets 27. 7

These inserts are used to form a part of the interlock arrangementbetween the chuck and the abrasive ring 1.

. Each insert 25 is drilled with an elongated hole 29. The

hole may be formed by use of a combined end mill and side-milling cutterwhich is first drilled through to form a hole. .Then the insert is movedabout a radius equal to the radius taken from the center of the chuck,so that the elongated hole 29 has sides which are segments of" holds foreasy removal of abrasive ring 1.

Once the magnets 21 and the inserts 25 have been set and fastened inplace (but before rubber bushings 28 i have been pressed in), the spacesbetween the magnets and in the yokes of the magnets, etc., are allfilled with a suitable .filler,, such as a thermosetting plastic 26. Ithas been found that a thermosetting plastic which sets at about 300 F.is suitable, and the plastic is mixed with aluminum powder or the liketo produce a more durable surface and to reduce cost. .After the spaceshave been filled and the plastic has been set by curing, a grinding cutis taken across the whole surface so that pole faces of magnets 21, thefaces of inserts 25, and the filler 26 are all flush and flat.

Within each elongated hole 29, a rubber bushing 28 is inserted havingrelatively thin side walls and thicker end walls. Clearanceis providedat the upper end of the rubber bushings to permit the rubber to deformwithout flowing up-against then'ng 1. The purpose of these bushings isto permit. interlocking pins or studs 5, which are fixedly mounted toring 1,-to move somewhat in response to torsional stress brought aboutby actual grinding operations. While in Fig. 3 the studs 5 are shown ina central position, under running conditions the ring 1 and the studs 5are displaced by the drag of a workpiece against the abrasive ring, sothat the studs 5 push against one or the other ends ofthe rubber bushing2 3 depending, of course, upon the directionof rotation. In responsetothelittle shocks set up as the diamond particles encounter a workpiece,ring 1 is displaced rotationally, and this-displacement is cushioned bythe resiliency of rubber bushing-28. Thestrength of the magneticattraction is appropriately adjusted by the size and strength of themagnets-and-bythe-flux path-provided through ring 1, sothat-some-slight'amountof slippage in response to grinding shock ispermitted.

There are many'alternative variations of accomplishing this same result.For'example, as" shown in Fig. 4, the insert elements 25" may be'omitted and an annular groove 41 provided;'falling within'the yokes ofthe magnets. The groove is of a depth and width to accommodate pins 5.If necessary, the pins may be made smaller and shorter than shown to fitwithin the groove. The groove is preferably defined by an annular,U-shaped, brass member 43, as shown in Figs. 4 and 5. This provides asmooth and durable engaging surface. If desired, the plurality ofindividual magnets may be replaced with a single, continuous, circular-U-sectioned magnet magnetized in such a way that the inner limbconstitutes one pole and the outer limb constitutes another, and, ifdesired, the yoke section of such a magnet may serve as the interlockinggroove for registry with a depending ring attached to ring 1. Or again,the wheel body 11 may be formed with the inner lip of themagnetreceiving groove 19 extending slightly above the level of themagnets and fitting closely inside ring 1.

What is characteristic of any of these arrangements is that some degreeof slippage is intentionally provided between an abrasive-bearing member1 and a more or less rigid wheel body 11, while at the same time theabrasive-bearing ring is held against the forces tending toward radialdisplacement and is given a firm backing against any substantial axialdisplacement. The ring must be free to yield to rotational shock. Itmust not yield to radial displacement, as if it did it would causeunbalance. And it must not yield to pressure against axial displacementexcept in minute degree. Of course, it is impossible to achieve perfectrigidity in any direction, but the intention is that the axial andradial displacement permitted be very small as compared with therotational displacement permitted.

Once the magnetic chuck of this invention is fitted to a grindingspindle and trued up, there is little occasion to need adjustment exceptin the case of abuse or accident. The operator is provided with a numberof the abrasive-bearing rings. All that the operator needs to do is toWipe the face of the chuck clean and likewise the mounting surface ofabrasive ring 1, which is then quickly slipped into place and isinstantly ready for use. During use, the slight amount of slippage whichis provided gives a soft feel to the grinding wheel and is helpful inimparting sharp edges to the workpieces where these are important. Theactual amount of slippage may be kept very small,.usually less than 1%of the wheels rotation,-and stillbe effective. Where rubber bushings areused, the slippage is restored aftereach shock by the resiliency oftherubber.

When the abrasive-bearing ring becomes worn so that it no longer cutsrapidly, or, in the case of a contoured ring for shaping purposes, whenthe desired contour is lost, it is only necessaryto slip the used ringoff the chuck, moving it axially to do so, and then to replace it with anew ring.

This saves time that would otherwise have to be spent in redressing aconventional wheel and, ultimately, in replacing it and, possibly,having to trueit up.

'The abrasive-bearing rings may readily be reclaimed. This isparticularly easy if the studs 5 (or whatever other interlocking membersserve their purpose) are made of the same material as ring 1. As thediamond particles wear flat on their protruding surfaces, so that thecutting speed of the tool decreases, the ring is removed from thegrinding machine and is returned in its entirety to the factory. Therings are cleaned and may then be used directly as anodes in anelectroplating bath for the making of new and additional tools,presumably of the same kind. As the metal of the abrasive-bearing ringsis dissolved into the plating bath, the diamond'particles which remainfall to the bottom of the container for the bath and may, fromtime totime, be recovered, washed, dried and rescreened. It is found that agreat many of the particles may beused again without any disadvantagewhatsoever, for it is very unlikely that any substantial number of theparticles will be aligned in new tools with the surfaces flattened-byprevious use .in cutting position. As a practical matter, thereclaimed diamond particles are usually used in a mixture with newdiamond particles. One of the reasons for preferring to use studs 5which are made of the same material as ring 1 and for using weldingrather than soldering to attach them is that in this way it is notnecessary to remove the studs and to clean away the solder before thereclaiming begins. The reclaiming is particularly desirable, of course,where the material used is nickel or other material which hassubstantial value and may, from time to time, be in short supply.

Thus, there is provided a means for using very fastcutting,diamond-bearing abrasive tools, of manufacturing them at very low cost,of using them with a very minimum of loss of time in dressing orchanging tools and with a maximum saving of material.

While a preferred embodiment of this invention has been shown anddescribed, it will be apparent that numerous modifications andvariations thereof may be made without departing from underlyingprinciples of the invention. It is therefore desired by the followingclaims to include within the scope of the invention all such variationsand modifications by which substantially the results of this inventionmay be obtained through the use of substantially the same or equivalentmeans.

What I claim as new and desire to secure by Letters Patent is:

1. As a new article of manufacture, a grinding wheel assembly comprisinga magnetic chuck adapted to be mounted on, and driven by, a power drivenshaft and consisting of a disc-like body provided on the central portionthereof with means for connecting it to the shaft and embodying on itsouter marginal portion a laterally extending ring-shaped enlargementhaving formed therein a comparatively deep concentric annular groove andprovided with means forming a smooth fiat annular driving surface inconcentric relation with the chuck body and at the side of the groovethat is farther from the chuck body, an annular series of separatelyformed spaced apart permanent magnets mounted fixedly in the groove andarranged so as to set up attraction-type magnetic lines of force throughthe driving surface, a removable separately formed lightweightring-shaped grinding member contoured substantially conformably to, andfitting normally 7 flatly against, the driving surface, retainedyieldingly in chuck body while at the same time permitting'the grindingmember to rotate relatively to the said chuck body about the lattersaxis, said permanent magnets being preand in which the mechanicalinterlock means for positively holding the grinding member againstradial displacement with respect to the chuck body serves also to limitrotative displacement of the ring-shaped grinding member with respect tothe chuck body and consists of a plurality of spaced apart elongatedarcuate holes which intersect and extend inwards from the drivingsurface, and a plurality of studs which are fixedly connected to theinner surface of and project at right angles to the ring of the grindingmember, correspond in number to and are associated respectively with theholes, project into the holes, and are so proportioned that they aremovable lengthwise of the holes in connection with rotative displacementof the grinding member with respect to said selected in such manner thattheir combined magnetic, l5 grinding surface.

power of attraction is so proportioned and correlated to the grindingmember that when a workpiece to be ground is initially and normallyplaced against the layer of abrasive particles in connection with aworkpiece grinding operation the grinding wheel in response to grindingshock is permitted to be rotatively displaced to a limited extent onlyrelatively to said driving surface.

2. A grinding wheel assembly according to claim 1 and in which the bodyof the magnetic chuck is formed of non-magnetic material and theabrasive particles of,

the ring-shaped grinding member are diamonds.

3. A grinding wheel assembly according to claim 1 and References Citedin the file of this patent UNITED STATES PATENTS Morrison June 1, 1875224,623 Allen Feb. 17, 1880 2,056,182 Gardner Oct. 6, 1936, 2,226,506Van Der Pyl Dec. 24, 1940 2,241,585 Day May 13, 1941 2,347,920 Mays May2, 1944 2,361,492 Pare Oct. 31, 1944 2,368,473 Keeleric J an. 30, 19452,388,020 Suwa Oct. 30, 1945 2,408,220 Lum Sept. 24, 1946 2,424,140Beecher July 15, 1947 2,496,352 Metzger Feb. 7, 1950 2,505,196 Mays Apr.25, 1950 4, 2,506,556 Ball et a1 May 2, 1950

